BoilerFaultCodesYour boiler has lost power while it was already trying to report a different fault, which has confused the system control board.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Power failure during failure shutdown.
What causes this fault?
This fault occurs when the boiler experiences a sudden loss of electrical power at the exact moment it was already attempting to shut down due to a different internal issue. This sequence confuses the control board because it cannot properly record the initial problem before the power cuts out. The most common reasons are a loose electrical connection, a blown fuse, or a faulty main circuit board that can no longer manage the power supply.
This fault can be more frequent during stormy weather if localized power surges or 'brownouts' cause the boiler to lose power unexpectedly.
DIY fix possible
Check if there has been a recent power cut or if a fuse has tripped in your home.Turn the boiler power switch off and then back on again to reset the electronics.If the code persists, check if another fault code appears briefly before the 04 code displays.
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A boiler cover plan would cover faults like 04 — no call-out fees, no surprises.
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Parts for discontinued models can be hard to find and expensive. A new A-rated boiler could save you money on both repairs and energy bills.
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